The present invention is directed to a laser fluid control apparatus and method for precisely controlling the fluid flow to a laser. The volume and/or composition of the fluid supplied to the laser can be selectively and precisely varied during the operation of the laser by means of a programmable control means of the apparatus.
It is necessary to provide a fluid such as a gas to the resonator of a laser before the laser can be operated by exciting the gas within the cavity to produce a laser beam. Laser gas must also be supplied to the laser during the operation of the laser in order to replenish or maintain the gas within the laser for continued operation of the laser due to degradation and losses of the gas from, for example, vacuum leaks and chemical reactions which occur with the gas during the operation of the laser. The volume at which the gas is supplied to the laser and also its composition can effect operating characteristics of the laser, such as the power of the laser, and also the cost for operating the laser. It has been found that relatively long warm-up times for lasers reduce the efficiency or cost effectiveness of their use. Optimal gas mixes have also been found to vary for different power levels and modes of laser operation such as for laser pulse performance as compared to continuous wave laser operation.
An object of the present invention is to provide a fluid flow control apparatus and method for precisely controlling the flow of a fluid to a laser which enable the laser operator to readily enhance the laser performance and operating efficiency. More particularly, the invention allows the laser operator to select in advance or at any time during the operation of the laser the various fluid requirements for economy, fast warm-up time and laser performance by providing a programmable control means which the operator can initially set so that the apparatus automatically selectively and precisely varies the volume and/or the composition of the fluid supplied to the laser at predetermined time intervals during operation of the laser. Predetermined accurate adjustments in the volume and/or composition of the fluid being supplied to the laser can also be conveniently made by the operator with the control means during the operation of the laser.
According to a disclosed preferred embodiment, the fluid flow control apparatus of the invention for precisely controlling the flow of fluid to a laser from a supply of the fluid comprises fluid passage means extending between a supply of fluid and the laser, valve means located in the fluid passage means, the valve means being adjustable relative to the fluid passage means for controlling the flow of the fluid from the supply to the laser, and control means for adjusting the valve means and thereby the volume of the fluid supplied from the fluid supply to the laser. The apparatus and method may be used, for example, to provide a high volume of the fluid to the laser when the laser is cold for a quick warm-up of the laser and a reduced volume of the fluid to the laser after the laser has warmed-up for more economical operation of the laser. The control means provides the high volume of the fluid to the laser for a predetermined period of time before reducing the volume. The operator can manually override automatic timers of the apparatus as referred to below, or a computer could otherwise control the timers.
The control means in the disclosed embodiment adjusts the valve means to open and close or otherwise adjust the gas passage means at some frequency for controlling the volume of the fluid supplied to the laser. As a first frequency, the valve means is actuated to keep the passage means open during the entire predetermined period of time for warm-up of the laser for effecting the high volume of the fluid to the laser. This period of time is set by a first timer means of the apparatus. A second timer means adjusts the valve means to alternately close and open or otherwise adjust the fluid passage means to provide the reduced volume after expiration of the predetermined period of time. More particularly, the second timer means includes an OFF timer and an ON timer for respectively, alternately controlling the periods of time when the valve means closes and opens the fluid passage means. The operator can adjustably select at least the frequency that the ON timer maintains the valve means in a position to open the fluid passage means for varying the volume and/or composition of the fluid to the laser. The valve means in the disclosed embodiment is controlled by a variable frequency timer which controls at least one admit valve which is moved to open and close the fluid passage means by a solenoid which is actuated by the control means of the apparatus.
The fluid flow control apparatus further includes means for maintaining the fluid pressure in the laser substantially constant even during the adjustments in the volume and/or composition of the fluid being supplied to the laser. In the illustrated embodiment a working pressure control valve switches between two flow control valves to selectively direct the exhausted fluid through one of the two flow control valves to maintain the fluid pressure in the laser substantially constant even as the programmable control means of the invention selectively varies the volume and/or composition of the fluid being supplied to the laser.
The fluid which is supplied to the laser is typically a gas which is composed of several gases which are mixed by the apparatus before being supplied to the laser. The supply of the mixed gas itself can be controlled with the apparatus and according to the method of the invention or, as in the disclosed, preferred embodiment, the supplies of the several component gases of the laser gas are each separately controlled to conveniently permit variation of the composition, as well as the volume of the gas supplied to the laser. Thus, according to the disclosed embodiment, the apparatus includes a plurality of supplies of respective fluids and a plurality of respective passage means between the supplies and the laser. The valve means includes a plurality of respective valve means in respective ones of the plurality of passage means for controlling the fluids supplied to the laser from the supplies of fluids. The control means automatically adjusts the plrrality of valve means to control the respective fluids supplied to the laser from the plurality of supplies of fluids. A means for mixing a plurality of respective fluids together before the fluids are supplied to the laser resonator is provided. The apparatus also allows the operator to conveniently select special gas mixtures for pulsed or continuous wave modes of operation for the laser by actuating a switch on the apparatus to change the gas composition supplied to the laser.
The disclosed method of the invention involves selectively and precisely varying at least one of the volume and the composition of the fluid supplied to the laser. In one embodiment of the method this involves supplying a fluid at a relatively high volume to the laser during an initial operating period of the laser for a quick warm-up of the laser and supplying the fluid at a reduced volume to the laser after the laser has warmed up for economical operation of the laser. This method of the invention is particularly advantageous in that it can significantly reduce warm-up time and gas consumption.
Further, according to the method, the laser gas is supplied at the reduced volume by alternately opening and olosing at least one gas admit valve at predetermined time intervals in response to the operation of a programmable control means. The high volume of the fluid to the laser for warm-up and highest power output is provided by maintaining at least one gas admit valve open during the entire initial operating period of the laser. The reduced volume of the laser gas is predetermined by the operator or controller such as a computer by selectively adjusting the length of the time intervals which the at least one gas admit valve remains open relative to the time intervals it remains closed. This is accomplished with the programmable control means of the invention prior to initiation of operation of the laser. Alternatively, another's computer could be used to control the timers of the apparatus in the manner disclosed herein. Where several gases are controlled, the gas composition can also be programmed. The operator can change the composition of the gas to be supplied to the laser either prior to or during operation of the laser by selecting a continuous wave (CW) mode of operation, a pulsed mode of operation or other mode of operation for the laser. In the disclosed embodiment, selecting the pulsed mode of operation changes the N2 contnnt of gas supplied to the laser for improving the laser performance.
These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings, which show, for purposes of illustration only, one embodiment in accordance with the present invention.